Back ground : Endometrioid carcinoma with yolk sac differentiation is very rare and there are few reports on its cytologic features.

Case : A 36-year-old woman was admitted to our hospital with the complaint of irregular vaginal bleeding. An endometrial smear revealed carcinoma cells with unclear cytoplasmic margins containing small round nuclei with reticular chromatin. Cytological diagnosis was difficult, but a protruding tumor was recognized macroscopically in the uterine cavity. The tumor was finally diagnosed as endometrioid carcinoma with yolk sac differentiation from its histopathologic and immunophenotypic features, which included immunohistochemical positivity for SALL4 and Glypican3.

Conclusion : The cytological features seen in this case needed to be differentiated from those of grade 1 endometrioid carcinoma, clear cell carcinoma, and dysgerminoma.

Background : Renal collecting duct carcinoma is also called carcinoma of the Bellini duct. It is extremely rare among renal tumors and carries a very poor prognosis. Therefore, accurate diagnosis and early treatment are important. Herein, we report a case of renal collecting duct carcinoma, diagnosed by rapid intraoperative stamp cytology.

Case : A woman in her 70s visited our hospital complaining of abdominal pain. Abdominal CT revealed multiple enlarged lymph nodes extending from around the abdominal aorta to the bilateral iliac arteries, suggesting the possibility of malignant lymphoma. Other findings included low-density areas in the liver and right kidney. As malignant lymphoma was suspected clinically, intra-abdominal lymph node resection was performed. On the basis of rapid intraoperative stamp cytology, the tumor was diagnosed as an adenocarcinoma, as it showed malignant cells in a tubular or acinar arrangement, nucleus size anisotropy, and extensive nuclear fission. The diagnosis was confirmed by histopathology. Subsequent renal biopsy with immunohistochemical analysis led to the final diagnosis of renal collecting duct carcinoma.

Conclusion : In this patient, we were able to demonstrate the cytological characteristics of renal collecting duct carcinoma using stamp cytology material from a metastatic lymph node.

Background : Differentiating pleural mesothelioma from lung cancer often requires cytological analysis of the pleural fluid. However, coexistence of the two cancers is rare, and studies reporting the cytological findings of both cancers coexisting within a single individual are scarce. In this case report, we present the case of a patient in whom cytological examination of the pleural fluid revealed both mesothelioma and lung adenocarcinoma cells.

Case : A man in his 70 s with a history of smoking visited a nearby hospital with the chief complaint of breathlessness. Lung cancer was suspected, and the patient was referred to our hospital for further examination. Cytological examination of the pleural fluid revealed multiple scattered large cells that were binucleate and exhibited hump-like cytoplasmic projections. Immunohistochemical analysis of a pleural fluid cell block confirmed positive immunostaining of the mesothelioma-derived cells for calretinin, WT-1, and CK5/6. In addition, a small number of adenocarcinoma cells showing positive staining for TTF-1- and CEA were also observed, indicating the coexistence of mesothelioma and lung adenocarcinoma cells.

Conclusion : Mesothelioma cells and lung adenocarcinoma cells rarely occur in the same specimen. Immunostaining, molecular-biologic analyses, and pleural fluid cell block analysis may be useful to enhance the diagnostic accuracy of pleural fluid cytology in such patients.

Background : We report a case of malignant mesothelioma detected by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA).

Case : A male in his 60s presented to his local doctor with a history of cough, sputum, and dyspnea on exertion. Imaging examination led to the suspicion of pleural mesothelioma and the patient was referred to our hospital. Chest computed tomography revealed diffuse thickening of the left pleura with irregularities, encapsulated pleural effusion, and multiple enlarged lymph nodes. Cytologically, atypical cells were seen in papillary arrangement with a high N/C ratio or in loose sheet-like clusters with a moderate N/C ratio. The nuclei of the atypical cells were centrally located, and the cells were either mono-or binucleated containing thick polygonal cytoplasm, with cell-to-cell apposition and window-like crevices. Small orange G-positive cells were also observed. Histologically, numerous cell clusters in papillary, micropapillary, and sheet-like arrangements, nuclei with mild irregularities and distinct nucleoli, and binuclei were observed. The results of immunohistochemical analysis supported the diagnosis of malignant mesothelioma.

Conclusion : Although the diagnosis of mesothelioma using EBUS-TBNA may differ from the characteristic findings in fluid specimens, the appearance of small orange G-positive cells may be suggestive of mesothelioma.

Background : T lymphoblastic lymphoma (T-LBL) frequently manifests with a mediastinal mass and pleural effusion. We report a case of early T-cell precursor lymphoblastic lymphoma (ETP-LBL) in which pleural fluid cytology showed more than 5% basophils in a background of atypical cells.

Case : A 14-year-old male patient with a past history of allergy presented with a prolonged history of cough and low-grade fever. A plain chest X-ray revealed pleural effusion and a mass lesion in the anterior mediastinum. Pleural fluid cytology showed atypical cells with fine granular chromatin, which led us to suspect a malignancy of lymphocytic origin. An increase in the number of basophils (7.3% of nucleated cells) was observed in the background. Immunohistochemical staining (IHC) of a pleural fluid cell block and mediastinal biopsy sections revealed atypical cells that showed positive staining for CD3 and CD99, and negative staining for CD4/CD8 and TdT. Bone marrow infiltration of less than 25% suggested the diagnosis of T-LBL. It was further classified as ETP-LBL because the atypical cells showed negative staining for CD1a and CD5, and weakly positive staining for CD117.

Conclusion : The differential diagnosis of lymphoma using IHC staining is crucial as determining the high-risk type of lymphoma is important for selecting the appropriate treatment. On the other hand, in our present case, the finding of basophilic pleural effusion was not directly related to the T-LBL diagnosis, and we considered the possibility of local infiltration of basophils associated with the tumor.